Water treatment using ultraviolet (UV) radiation offers many advantages over other forms of water treatment, such as chemical treatment. For example, treatment with UV radiation does not introduce additional chemical or biological contaminants into the water. Furthermore, ultraviolet radiation provides one of the most efficient approaches to water decontamination since there are no microorganisms known to be resistant to ultraviolet radiation, unlike other decontamination methods, such as chlorination. UV radiation is known to be highly effective against bacteria, viruses, algae, molds and yeasts. For example, hepatitis virus has been shown to survive for considerable periods of time in the presence of chlorine, but is readily eliminated by UV radiation treatment. The removal efficiency of UV radiation for most microbiological contaminants, such as bacteria and viruses, generally exceeds 99%. To this extent, UV radiation is highly efficient at eliminating E-coli, Salmonella, Typhoid fever, Cholera, Tuberculosis, Influenza Virus, Polio Virus, and Hepatitis A Virus.
Intensity, radiation wavelength, and duration of radiation are important parameters in determining the disinfection rate of UV radiation treatment. These parameters can vary based on a particular target culture. The UV radiation does not allow microorganisms to develop an immune response, unlike the case with chemical treatment. The UV radiation affects biological agents by fusing and damaging the DNA of microorganisms, and preventing their replication. Also, if a sufficient amount of a protein is damaged in a cell of a microorganism, the cell enters apoptosis or programmed death.
Ultraviolet radiation disinfection using mercury based lamps is a well-established technology. In general, a system for treating water using ultraviolet radiation is relatively easy to install and maintain in a plumbing or septic system. Use of UV radiation in such systems does not affect the overall system. However, it is often desirable to combine an ultraviolet purification system with another form of filtration since the UV radiation cannot neutralize chlorine, heavy metals, and other chemical contaminants that may be present in the water. Various membrane filters for sediment filtration, granular activated carbon filtering, reverse osmosis, and/or the like, can be used as a filtering device to reduce the presence of chemicals and other inorganic contaminants.
Mercury lamp-based ultraviolet radiation disinfection has several shortcomings when compared to deep ultraviolet (DUV) light emitting device (LED)-based technology, particularly with respect to certain disinfection applications. For example, in rural and/or off-grid locations, it is desirable for an ultraviolet purification system to have one or more of various attributes such as: a long operating lifetime, containing no hazardous components, not readily susceptible to damage, requiring minimal operational skills, not requiring special disposal procedures, capable of operating on local intermittent electrical power, and/or the like. Use of a DUV LED-based solution can provide a solution that improves one or more of these attributes as compared to a mercury vapor lamp-based approach. For example, in comparison to mercury vapor lamps, DUV LEDs: have substantially longer operating lifetimes (e.g., by a factor of ten); do not include hazardous components (e.g., mercury), which require special disposal and maintenance; are more durable in transit and handling (e.g., no filaments or glass); have a faster startup time; have a lower operational voltage; are less sensitive to power supply intermittency; are more compact and portable; can be used in moving devices; can be powered by photovoltaic (PV) technology, which can be installed in rural locations having no continuous access to electricity and having scarce resources of clean water; and/or the like.
FIGS. 1A-1C and FIGS. 2A-2B illustrate previous applications where the UV disinfection systems are based on mercury lamps. One of the important issues associated with mercury lamps is that it is difficult to turn on and off such a device rapidly. As such, the intensity levels of mercury lamp are sub-optimal for devices that require rapid turn-on/turn-off times. FIG. 2B further illustrates a mixing element for creating a turbulent flow in the device. The turbulent flow promotes mixing and improves radiation exposure of the fluid.